Effect of solvent type on the formation of tubular fullerene nanofibers

1D Fullerene C₆₀ nanofibers (FNFs) were prepared via liquid-liquid interfacial precipitation (LLIP) using toluene, m-xylene, pyridine and/or N-methyl-2-pyrrolidone (NMP) as solvents and isopropyl alcohol as the precipitation agent at 8 °C. C₆₀-saturated solutions were exposed to visible light to promote the growth of FNFs. When the solvents were toluene and m-xylene, it was difficult to synthesize hollow C₆₀ fullerene nanotubes (FNTs). By contrast, the hollow FNTs were easily grown in the C₆₀-pyridine solution or C₆₀-NMP solution upon exposure to visible light. It is found that there is a critical correlation between the adducts of the solvents with C₆₀ molecules and the tubular structure of FNFs.     

On the morphology of SrCO<Subscript>3</Subscript> crystals grown at the interface between two immiscible liquids

In this paper we report on the growth of strontianite crystals at the interface between an aqueous solution of Sr²⁺ ions and organic solutions of chloroform and hexane containing fatty acid/fatty amine molecules by reaction with sodium carbonate. When fatty acid was used as an additive at the interface, the crystals grown were self-assembled needle shaped strontianite crystallites branching out from the seed crystal via secondary nucleation. Under identical conditions of supersaturation, the presence of fatty amine molecules at the liquid-liquid interface resulted in needle shaped strontianite crystals with spherical crystallites arranged around central needles. This clearly indicates that the functionality of the head group of the amphiphiles at the liquid-liquid interface affects the morphology of the strontium carbonate crystals formed. The use of interfacial effects such as dielectric discontinuity, polarity and finite solubility of the two solvents etc opens up exciting possibilities for tailoring the morphology of crystals at the liquid-liquid interface and is currently not possible in the more popular crystal growth with similar amphiphiles at the air-water interface.     

液-液界面生长法制备C_(60)晶体

常温常压下利用液-液界面生长法制备了不同形貌的C60晶体,并对其生长机理进行了初步探讨。采用扫描电镜和X射线衍射分别对晶体形貌和结构进行了表征,结果表明,在CS2-异丙醇两相界面上可以生长形貌均匀的棒状晶体,且获得的晶体结构为简单六方。     

具有层状碱金属盐结构的氢氧化氨基苯甲酸锌的制备及表征

以自制的β-Zn(OH)2和氨基苯甲酸为原料,水热合成了具有层状碱金属盐(LBMS)结构的氢氧化氨基苯甲酸锌化合物。通过XRD、TG-DTA、SEM和TEM分析研究了合成产物的结构、形貌和热稳定性,探讨了合成条件对水热反应产物的影响及合成产物在有机溶剂中的剥离反应。当o-NH2C6H4COOH/Zn的摩尔比为1.2,水热温度70℃下反应12h时,得到的层状物具有板块状粒子特征,层间距为1.33nm;当m-NH2C6H4COOH/Zn的摩尔比为1.8,水热温度40℃下反应24h时,得到的层状化合物具有纤维状粒子特征,层间距为1.08nm。合成的层状物在醇溶剂中可发生剥离反应,层状氢氧化邻氨基苯甲酸锌在正丁醇中的剥离量为0.12g.L-1,层状氢氧化间氨基苯甲酸锌在乙醇中的剥离量为0.18g·L-1。     

Composite of DGEBA/TBA epoxy blend and amine-functionalized carbon nanotube: Structural,thermal, nonflammability,and EMI shielding studies

Novel blend of diglycidyl ether of bisphenol-A (DGEBA) and tetrabromo bisphenol-A (TBA) was reinforced with acid-functionalized (MWCNT-F) and amine-functionalized multi-walled carbon nanotube (MWCNT-A). DGEBA/MWCNT-A displayed fine tubular morphology with open nanotube ends, while DGEBA/TBA/MWCNT-A displayed somewhat aggregated morphology due to lesser filler content. DGEBA/TBA/MWCNT-A system showed maximum enhancement in decomposition temperature (T₀ = 404°C, T_max = 583°C). Glass transition temperature and Limiting oxygen index of DGEBA/TBA/MWCNT-A were also higher (221°C and 55%) compared with other systems. DGEBA/TBA/CNT-A 0.1 had crystalline morphology with diffractions at 12.7° and 26.09°. Novel nanocomposite revealed EMI shielding effectiveness of ～15.05–15.18 dB, i.e., suitable for aerospace applications.     

间苯二甲酸共聚酯的结晶特性

研究了聚对苯二甲酸乙二醇酯（PET）分子链中引入间苯二甲酸（IPA）的无规共聚酯（IPET）的非等温结晶动力学和等温结晶时球晶的生长和形态。结果表明,共聚酯的结晶温度随IPA含量的增加而升高,玻璃化转变温度、熔点随IPA含量的增加而降低;IPA的引入使IPET的结晶速率及球晶生长速率明显降低,但对球晶的形态及生长机理并无明显的影响。     

Growth and Characterization of C60 Crystals from Pure C60 and Fullerite

Good quality C₆₀ crystals have been grown from high purity C₆₀ powder and fullerene mixture (C₆₀/C₇₀) by vacuum sublimation method. The grown crystals were characterized with Optical microscopy, SEM, powder XRD, High Performance Liquid Chromatography and Raman spectroscopic analyses.     

Sublimation epitaxy of AlN layers on 4H-SiC depending on the type of crucible

Epitaxial layers of aluminum nitride ≤335 μm thick have been grown at temperatures of 1900 and 2100 °C on 10×10 mm² (0 0 0 1)-oriented α(4H) silicon carbide (SiC), with growth times of 1 and 4 h, via sublimation-recondensation in a RF-heated graphite furnace. The source material was polycrystalline AlN. The sublimation process was performed in three types of graphite (C) crucible: C1, C2 with inner diameters of 35 and 51 mm, respectively, and C3 with the same inner diameter as C1, but coated with a layer of TaC. The surface morphology reflects the hexagonal symmetry of the substrate, suggesting an epitaxial growth for samples grown in C1 and C3 crucibles for all growth conditions. The same symmetry is observed for AlN layers grown in the C2 crucible, but only at 2100 °C. X-ray diffraction analyses confirm the epitaxial growth of AlN samples with the expected hexagonal symmetry. A high-resolution X-ray diffractometer was used to assess the quality of the single crystals. A full width at half maximum of 242 arcsec was achieved for an AlN layer grown in the crucible coated with TaC.     

On the growth of neodymium pentaphosphate crystals for laser action

The growth of Nd_xLa_1?xP₅O₁₄ (0 ≤ x ≤ 1) crystals from phosphoric acid solution has been studied. Crystals have been obtained at temperatures between 300°C and 750°C. Vitreous graphite is a suitable container for the crystal growth. Changes in crystal morphology and crystal quality with growth temperature have been observed. Evaporation at high temperatures (>550°C) in an open system is too rapid to allow the growth of high quality crystals, although large (> 1 cm) crystals may be prepared, and the best quality crystals with respect to optical inhomogeneities are prepared at 450–550°C. Both pulsed and cw laser action have been observed. The Nd³⁺${}^4\text{F}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ fluorescent lifetime increases from 120 μsec (x = 1) to μsec (sec ≤ 0.05). These values indicate a seven-fold reduction in fluorescence quenching with respect to YAG:Nd. For crystals grown at temperatures below 600°C, however shorter lifetimes are observed and the quenching becomes more severe as the temperature of preparation is lowered. The quenching may be removed by appealing low lifetime crystals at 600–700°C in a P₂O₅ atmosphere. It is proposed on the basis of infrared absorption measurements that the lifetime shortening is related to the presence of hydrogen in crystals grown at lower temperatures. The vibrational characteristics of pentaphosphate crystals have also been investigated by Raman spectroscopy.     

强碱弱酸盐溶液对单晶硅太阳能电池表面织构化的影响

对晶向为（100）的p型单晶硅片进行表面刻蚀,制作减反射绒面。本实验是在传统氢氧化钠-异丙醇混合液中分别加入不同浓度的醋酸钠溶液、硅酸钠溶液和碳酸钠溶液对单晶硅片进行刻蚀。实验发现：分别加入醋酸钠溶液、碳酸钠溶液并没有在降低表面反射率方面起到很大作用,而只有加入硅酸钠溶液降低了表面反射率,有利于形成较好的腐蚀绒面。因此...     

Preparation of a crack-free rough titania coating on stainless steel mesh by electrophoretic deposition

TiO₂ (anatase) coating was prepared on stainless mesh by electrophoretic (EPD) process utilizing an isopropyl alcohol (IPA)-based suspension with submicron TiO₂ powder. When the deposition time was 30 s, a smooth thin coating was obtained. It remained crack-free even after sintering. Coating surface morphology was roughened by UV pre-illumination of the suspension. Photocatalytic decomposition of IPA to acetone and resultant electrochemical reaction at cathode during EPD provides heterogeneous deposition.     

气体压强对氮气氛下制备的C60纳米薄膜形貌和光学性质的影响

用扫描电镜、双光束紫外 可见分光光度计和椭偏仪研究了在氮气 (N2 )氛下制备的C6 0 薄膜的表面形貌及光吸收特性。研究发现 ,薄膜表面粒子粒径随气压的增大而增大 ,表面结晶现象也随气压增大而明显 ;与真空中制备的C6 0 薄膜比较 ,发现其紫外 可见吸收的相对强度明显不同 ,吸收峰位红移 ;并且随着氮气压强的增加吸收峰位红移增加。对氮气氛下C6 0 薄膜的形成机理及光吸收特性进行了讨论     

The effect of surfactants on the morphology and optical properties of precipitated wurtzite ZnO

Wurtzite ZnO crystals were prepared in aqueous solutions with additive-free and additives of sodium dodecyl sulfate (SDS), hexamethylenetetramine (HMT), cetyltrimethylammonium bromide (CTAB), and CTAB/SDS. In all cases, the obtained crystals exhibited the crystal structure of wurtzite ZnO and photoluminescence at UV and yellow regions. The ZnO crystals grown in the HMT solution have a morphology of aggregated rods. In the CTAB solution, rods and nanoparticles of ZnO crystals are obtained and their sizes are smaller than those obtained in other solutions. A unique morphology of aggregated nanosheets was observed for ZnO crystals grown with the mixture of CTAB/SDS. The origin of morphology difference of the ZnO crystals is explained by a chemical interaction between surface of ZnO seed crystal and ionized additives.     

Growth of large (111) and (1?1?1?) sodium bromate single crystals by Reverse Seeded Solution Growth method

Single crystals of sodium bromate with large size (111) and (1?1?1?) faces were grown from solution at a constant temperature of 35 °C by a new seeding technique called Reverse Seeded Solution Growth (RSSG) method. The average lateral and vertical growth rates of crystals grown by this method are 0.8 mm/day and 0.35 mm/day respectively, which results in thick crystal platelets. The grown crystals were characterized by chemical etching, UV-Vis and Vickers microhardness studies. Anisotropy in hardness has been observed for (111) and its opposite (1?1?1?) faces due to non-centrosymmetric nature of the crystal. The results show that crystals grown by RSSG method have better optical transmittance and hardness.     

Hydrothermal treatment of electric arc furnace dust

In this study, ZnO crystals were fabricated from electric arc furnace dust (EAFD) after alkaline leaching, purification and hydrothermal treatment. The effects of temperature, duration, pH, and solid/liquid ratio on ZnO crystal morphology and size were investigated. Results show a high reaction temperature capable of accelerating the dissolution of ZnO precursor, expediting the growth of 1D ZnO, and increasing the L/D ratio in the temperature range of 100-200°C. ZnO crystals with high purity can also be obtained, using the one-step hydrothermal treatment with a baffle that depends on the different solubility of zincite and franklinite in the hydrothermal conditions.     

Expanding production regions of α-form and β-form glycine using an antisolvent crystallization method assisted by N2 fine bubbles

To develop a crystallization technique that can enhance the production of metastable α-form and unstable β-form glycine, we studied the antisolvent crystallization of glycine using the gas–liquid interfaces around N₂ fine bubbles as novel crystallization fields. In the regions near the gas–liquid interfaces, local supersaturation is generated because of the accumulation of glycine and alcohol as an antisolvent as a result of the negative electric charge on the fine bubble surface. Hence, the produced glycine polymorphs change from the stable γ-form to a α-form or β-form glycine. Additionally, local supersaturation at the gas–liquid interfaces can be expected to change via modification of the accumulation of the glycine and alcohol molecules and the interaction of glycine-water-alcohol with the different alcohol additives. At a solution temperature of 303?K, methanol (MeOH), ethanol (EtOH), or isopropanol (IPA) as an antisolvent were rapidly mixed into the saturated glycine solution. While mixing MeOH, EtOH, or IPA with the saturated glycine solution, N₂ fine bubbles with an average size of 10?µm were continuously supplied to the mixed solution using a self-supporting bubble generator and a glycine polymorph was crystallized within 5?min. For comparison, an antisolvent crystallization free of N₂ fine bubbles was conducted using a propeller type mixer. During antisolvent crystallization with/without fine bubble injection, the additional alcohol volume was varied to control the generation rate of the supersaturation in the bulk solution (r_C/CS). Consequently, the production regions of the α-form and β-form glycine were broadened to lower r_C/CS via N₂ fine bubble injection. The expansion behavior for α-form or β-form glycine significantly increased because of the enhancement of local supersaturation at the regions near the gas–liquid interfaces of the N₂ fine bubbles owing to the decreasing carbon number in the alcohol.     

Growth of gallium orthophosphate single crystals in acidic hydrothermal solutions

The hydrothermal growth of GaPO₄ single crystals has been studied in several solutions. Among many solutions, H₃PO₄, HCl and H₂SO₄ solutions were found to be effective solvents for the growth of GaPO₄ single crystals. Single crystals have been hydrothermally grown at temperatures over the range 210 to 290 °C in these solutions with seed crystals. HCl solution was found to be the most effective solvent in which to grow large single crystals. Morphologies of crystals grown at temperatures below 200 °C tended to be bounded by small major rhombohedral (1 0 ˉ1 1) faces. In the temperature range from 210 to 430°C, the crystals have morphologies bounded by prism (1 0 ˉ1 0), small major rhombohedral (1 0 ˉ1 1) and minor rhombohedral (0 1 ˉ1 1) faces, and grew with well developed basal (0 0 0 1) faces with increase in the growth temperature. Single crystals of GaPO₄ with lower dislocation density have been hydrothermally grown at 210 to 290°C in 3m H₃PO₄ solution.     

PSf-DMAc-醇类非溶剂体系中非溶剂沉淀能力的研究

对聚砜(PSf)-二甲基乙酰胺(DMAc)-醇类非溶剂构成的制膜体系的热力学特性进行了研究,计算出这些体系的双结点线,并用这些醇类非溶剂通过光散射法进行浊点滴定实验,浊点曲线与双结点线基本重合,验证了双结点线的计算结果.计算和实验结果均证实,不同的醇类非溶剂对PSf-DMAc溶液的沉淀能力依次为:水>丙三醇>1,2-丙二醇>乙醇>异丙醇>异丁醇>异戊醇;同时,以水及IBA作非溶剂为例,观察了所得膜的截面结构及性能:随非溶剂沉淀能力增强,膜由皮层较厚而致密的结构逐渐转变为皮层较薄的典型非对称膜结构;膜的通透率更高,选择性更低.所得膜结构和性能对双结点线和浊点实验得到的结果进行了验证.这些研究对不同组成的聚合物溶液实际成膜有一定的指导意义.     

Kinetically controlled fabrication of C60 1-dimensional crystals

Considering the current application of fullerenes in the field of organic semiconductor devices, the highly crystalline or single crystal fullerene nanostructures with controlled shape and size contains some breakthrough for improved efficiency. Recently, fullerene 1-dimensional nanostructures, including nanowhiskers and nanotubes, become attractive kind of materials since the development of liquid-liquid interface precipitation (LLIP) process. The LLIP process has critical advantage; the fabrication of highly crystalline, even single crystal, fullerene 1-dimensional nanostructures with simple apparatus. However, the fabrication fullerene 1-dimensional structures by LLIP process requires long process time from one day to several days. In order to overcome this drawback, a modified process from conventional LLIP process is suggested. In the modified LLIP process, the nucleation step and growth step were divided. For the nucleation step, saturated fullerene solution is mixed with small amount of alcohols such as 2-propanol or ethanol. For the controlled growth step, the fullerenes in the nucleated solution are precipitated by addition of alcohol, which is injected to the bottom of the solution with controlled flow rate. In this modified process, the shape of the precipitated fullerene crystals is critically dependent on the nucleation steps and the size is dependent on the precipitation rate. By combination of proper nucleation step and growth rate, a well defined fullerene 1-dimensional structures, of 200-500 nm width and of hundreds microm length can be fabricated within two hours. In addition, by controlling injection rate and degree of supersaturation, several types of 1-dimensional structures including micro-tubes can be prepared and, by changing solvent and alcohol, several shape of C60 crystals including polyhedral particles and plates can be prepared.     

Flexible Luminescent Hydrogen-bonded Organic Framework for the Separation of Benzene and Cyclohexane

A nonplanar phenothiazine derivative with three cyano moieties (PTTCN) is designed and synthesized to achieve functional crystals for absorptive separation of benzene and cyclohexane. PTTCN can crystallize into two kinds of crystals with different fluorescence colors in different solvent systems. The molecules in two crystals are in different stereo isomeric forms of nitrogen, quasi axial (ax), and quasi equatorial (eq). The crystals with blue fluorescence in ax form may selectively adsorb benzene by a single-crystal-to-single-crystal (SCSC) transformation, but separated benzene from a benzene/cyclohexane equimolar mixture with a low purity of 79.6%. Interestingly, PTTCN molecules with eq form and benzene co-assembled to construct a hydrogen-bonded framework (X-HOF-4) with S-type solvent channels and yellow-green fluorescence, and can release benzene to form nonporous guest-free crystal under heating. Such nonporous crystals strongly favor aromatic benzene over cyclohexane and may selectively reabsorb benzene from benzene/cyclohexane equimolar mixture to recover original framework, and the purity of benzene can reach ≈96.5% after release from framework. Moreover, reversible transformation between the nonporous crystals and the guest-containing crystals allows the material to be reused.